Evidence exists that human brain tumors are composed of heterogeneous cell populations that account for their pleomorphism, biological change toward increased malignancy over time, and the occurrence of mixed gliomas and gliosarcomas. Such heterogeneity may also be responsible for the relatively poor results achieved in the chemotherapy of patients harboring malignant gliomas. To date, chemotherapy has usually been limited to single agents and this form of treatment may permit overgrowth of resistant cell lines. In our laboratory, different human malignant brain tumors growing in athymic nude mouse brains have displayed different chemosensitivities to standard agents, suggesting variability among gliomas and perhaps among different cell lines within each glioma. We propose to clone out these heterogeneous cell populations in tissue culture from gliomas obtained from patients undergoing resections of their tumors. The clonal lines will be characterized by morphology (light and electron microscopy), biochemical markers (S100 protein, glial fibrillary acidic protein, glycerol-3-phosphate dehydrogenase, cyclic nucleotide phosphohydrolase), karyology, growth kinetics, chemosensitivity, and cell surface markers. The parent lines and clones will be inoculated intracerebrally and subcutaneously into athymic nude mice to determine in vivo morphology, growth kinetics and chemosensitivity. The clone lines will be cocultivated to determine if phenotypic expression for drug sensitivity is altered and, if so, whether by intercellular exchange of diffusible substances and/or by cell-cell communication. Finally, utilizing the chemosensitivity profiles of the individual clones and information from cocultivation, new chemotherapy combinations will be designed and tested on the parent lines in vitro and in vivo. An attempt will be made to correlate chemosensitivities with other characteristics to find early identifiable markers in order to suggest chemotherapy regimes for the patient as early as possible.